The 115 cardinals participating in the conclave will gather inside the Sistine Chapel to cast their ballots for the new pope of the Roman Catholic Church.

Alessandra TarantinoAP

The stage is now set for the opening act of one of the more spectacular and intriguing theatrical dramas on the planet: the election of a pope.

In Rome, TV camera crews have set up their positions on big platforms overlooking St. Peter's Square and the Vatican, where the secretive process will begin Tuesday.

Bookies are raking in bets, even though veteran Vatican watchers insist that no obvious front-runner has emerged from a wide field of possible candidates to replace Benedict XVI, the first pope to resign in nearly 600 years.

After a tsunami of scandals about clerical sex abuse and cover-ups, Vatican mismanagement and corruption — and more besides — this is the Roman Catholic Church's chance to generate some positive headlines as attention focuses on the mysterious workings of what's known as the conclave.

Conclave — from the Latin for "with a key" — is a historic term that refers to the fact that the cardinals charged with the task of electing a new leader of the world's 1.2 billion Catholics will do so locked within the Vatican.

Most of the 115 "cardinal electors" will be housed in two-room suites in a guesthouse run by nuns. The accommodation is, by all accounts, modest — three- rather than five-star.

On hand is a team of cooks, doctors (the average age of this group of cardinals is 72), priests (to take confession) and technicians to enforce a communications blackout, both in the guesthouse and the Sistine Chapel, where the balloting takes place. The Vatican is determined to prevent any outside interference — or news leaking out from a tweeting cleric.

"The phone doesn't work, the TV doesn't work. They have no e-mail, they have no Internet, they have no cellphones," says the Rev. Thomas J. Reese of the National Catholic Reporter, who is an authority on the workings of the conclave.

On Tuesday morning, the "cardinal electors" will celebrate Mass in St. Peter's Basilica. Then, mid-afternoon, they walk into the Sistine Chapel in procession while singing prayers, and take their places.

Within the chapel, the scene must surely be stunning — a throng of cardinals, wearing blood-red robes, sashes and crucifixes beneath the pulsating blue, silver and gold hues of the Renaissance frescoes that adorn the Sistine's vaulted ceiling.

"The cardinals recognize this is the most important thing they will ever do in their lives. This is the high point of being a cardinal," Reese says.

"In the Sistine Chapel, they are sitting in absolute silence with Michelangelo's Jesus at The Last Judgment staring down from them from the wall."

After the cardinals have sworn oaths — to observe the rules and maintain secrecy — everyone who is not part of the conclave is ordered out with the announcement "Extra omnes!" or "Everybody out!"

The cardinals likely will vote once Tuesday, writing their choice on a small ballot paper. They walk up, one by one, and deposit this in an urn on an altar.Papers are counted by three cardinals, one of whom reads out the names. A two-thirds majority is required.

After the first day, there are two ballots each morning and two each afternoon until a pope is elected.

Ballot papers are burned in a stove inside the Sistine Chapel that's connected to a chimney on the roof.

If there is no victor, the smoke — with the help of some chemicals — comes out black. White smoke signals a new man has been chosen.

That, at any rate, is what's supposed to happen.

"It's never worked all that well," Reese says. "I wish they'd test it and make sure it works before they go into the conclave, because last time the smoke came out gray. Everybody was [asking], 'Is it white? Is it black?' "

The selected candidate is asked if he accepts the post. He can, theoretically, refuse, though this is extremely unlikely. (Pope John Paul I is said to have come close, muttering, "No, oh, please no" when he was asked.)

He chooses his new name, the cardinals pledge obedience, and the new pontiff is then dressed in his white robes with the help of a tailor. Three sizes have been prepared: small, medium and large.

This is the moment when a cardinal appears on a balcony overlooking St. Peter's Square to announce the news.

"Everybody's cheering," says Monsignor Kevin Irwin, professor of liturgical studies at The Catholic University of America. "And he [the cardinal] says, 'I announce to you good news. We have a pope.' — in Latin."

The cardinal then gives the name of the new pope, who eventually appears on the balcony and delivers a blessing before the cheering crowds in St. Peter's Square, to Rome and the world beyond.

The concept of the conclave is believed to date back some 770 years, when the papacy was vacant for a year and a half because no one could agree who the next pope should be. The people and senators of Rome grew so fed up that they locked up the cardinals until they reached an agreement.

Over the centuries, some conclaves have lasted months. That is not expected this time — though nothing is certain. There is speculation about divisions among the cardinals, including between the Curia, which is the Vatican administration, and cardinals from elsewhere. But the last time a conclave dragged on beyond five days was in 1831.

So keep your eyes on that smoke.

Copyright 2013 NPR. To see more, visit http://www.npr.org/.

Transcript

AUDIE CORNISH, HOST:

From NPR News, this is ALL THINGS CONSIDERED. I'm Audie Cornish. Tomorrow is the big day at the Vatican. The conclave begins. One-and-fifteen Roman Catholic cardinals will be locked inside the Vatican to begin the business of electing a new pope. The conclave is a process drenched in history and ritual and it's complicated. We asked NPR's Philip Reeves to walk us through how it works.

PHILIP REEVES BYLINE: Decision don't get much bigger than this. This is about the world's oldest continuous absolute monarchy. The leader of nearly 1.2 billion Catholics will take charge of a church in deep crisis. His election rests on 115 cardinals.

FATHER THOMAS REESE THE NATIONAL CATHOLIC REPORTER: And then the cardinals recognize this is the most important thing they will ever do in their lives. This is the highpoint of being a cardinal.

BYLINE: Father Thomas Reese of the National Catholic Reporter has studied the conclave system. During the conclave, the cardinals live within the Vatican grounds in a big guesthouse run by nuns. Most have two-room suites. That sounds luxurious but it isn't, says Monsieur Kevin Owen, professor of liturgical studies at the Catholic University of America. He's been there.

REPORTER: The phone doesn't work, the TV doesn't work. They have no email, they have no internet, they have no cell phones, they have no - they don't even have snail mail.

BYLINE: Tomorrow at mid-afternoon local time, the cardinals will leave their guesthouse and go to the Vatican's Pauline(ph) Chapel nearby. From there they walk in procession to the Sistine Chapel singing as they go, says Owen.

IRWIN: They're singing pray for us to the litany of the saints. It's a mantra. I mean, they're singing a mantra as they walk into the Sistine Chapel.

BYLINE: Pause for a moment and imagine this scene - a throng of cardinals from across the planet wearing blood-red robes, sashes and crucifixes, gathering beneath the pulsating blues and golds of the Renaissance frescoes that adorn the Sistine's vaulted ceiling. Reese says, once they're all inside, you can hear a pin drop.

REPORTER: In the Sistine Chapel there's absolute silence. There they are sitting in silence with Michelangelo's Jesus, you know, at The Last Judgment staring down at them from the wall.

BYLINE: Late afternoon, the cardinals will likely vote once.

REPORTER: Each cardinal has a ballot in front of him. It's a very small piece of paper. At the top of it says, I vote for...

BYLINE: The cardinals disguise their handwriting as they write the name and fold the paper in half.

REPORTER: And then you hold it in the air as you march up one by one. And, of course, the reason you're holding it up in the air is to make sure everybody can see you're only voting once.

BYLINE: Each cardinal posts his ballot into an urn. The papers are counted by three cardinals. One reads out the names. To win you need a two-thirds majority. After the first day, there are two ballots each morning and two each afternoon until a pope's elected. After the voting, ballot papers are burnt in a stove inside the Sistine Chapel that's connected to a chimney on the roof. The eyes of the world are on that chimney.

If there's no winner, the smoke, with the help of some chemicals, comes out black. White smoke signals a new man's been chosen and has accepted the papacy. Or at least that's what's supposed to happen, says Reese.

REPORTER: It's never worked all that well. I don't know, you know, I wish they would test it and make sure it works before they go into the conclave because last time, the smoke came out gray. Everybody was, is it white, is it black?

BYLINE: When a pope's elected, St. Peter's biggest bell is also supposed to ring. Last time, that didn't quite go to plan either. Reese says the cardinal in charge was busy burning ballot papers, so he instructed a Swiss guard to call the bell ringer instead.

REPORTER: So the Swiss guard runs out and gets a place where his cell phone works and calls the guy and tells him, ring the bell. And he won't do it. He won't do it unless he hears from his boss. He's not going to make a mistake and ring the bell when there's no pope.

BYLINE: Eventually, after a considerable delay, someone in authority called the bell ringer.

REPORTER: And slowly we saw the bells start to move and that's the point at which we knew that a new pope had been elected.

(SOUNDBITE OF BELLS)

BYLINE: Meanwhile, helped by a tailor, the new pope climbs into his new white robes. Three sets have been prepared, small, medium and large. Irwin says last time, when Cardinal Joseph Ratzinger was elected, none fitted.

IRWIN: So they had to take him out of his cassock, put him into a black sweater and over that put a white alb, nothing special, and then the red garment because nothing fit. He wasn't wearing a cassock at all.

BYLINE: Now comes the moment when a cardinal appears on that balcony overlooking St. Peter's Square.

Everyone is cheering, et cetera. And he says, I announce to you good news, we have a pope.

IRWIN: And he goes on about eight or nine words that are titles, you know, the most reverend and the this and the that and then gives the person's first name.

BYLINE: That's when we discover who's the next pope before the man himself nervously walks out onto that balcony and meets an anxiously-awaiting world. Philip Reeves, NPR News, Rome. Transcript provided by NPR, Copyright NPR.